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I'm building a project I got as PCB+panel, sourcing my own parts. It takes a clock buffered through CD40106 and runs a CD4017. The sequential outputs of the CD4017 create a programmable sequence of voltages that go to an LM358-based output stage. The full schematic can be seen here. I just realized I didn't source the LM2931, which forms the +5V line for the digital ICs. I checked the datasheet and looks like it's just a low-dropout 5V regulator rated at 100mA. Should good old 78L05 fit the bill as a replacement for just powering 4XXX logic? I'm almost sure it should be fine but thought it's better to ask. Here's the relevant part of the schematic:

Schematic Also, I thought of using a TL072 instead of the LM358 as I have plenty of these.

I have tried contacting the PCB creator with a previous project also from him, but got no reply so I think I'll get everything sorted out quicker by just asking here and making some modifications on my own.

Edit: The LM358 stage is just the usual 100k/100k summing mixer for the CD4017 outputs and then 100k/100k buffer with 15pF in the feedback path and 330R at the output jack.

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As a regulator yes, it should give you the correct output. Some manufacturers datasheets suggest a 100 nF output capacitor on a 78L05 too.

Be aware though, you're dropping 7 V, the TO92 78L05 can't handle much power dissipation, so depending on your current draw you might want to step up to a TO220 part.

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  • \$\begingroup\$ I am aware of the fact it's a linear regulator capped at 100mA. The specified LM2931 is 100mA as well and in the same package. The current draw is literally a dual opamp, 5 LEDs and 2 logic chips. Both the circuit's outputs and inputs they're likely to be going to are certain to be buffered. \$\endgroup\$ – Qrchack Feb 22 '19 at 7:49

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